Ostomy appliances of the so-called "two-piece" type are well known and consist essentially of an adhesive faceplate for adhesive attachment to the peristomal skin surfaces of a patient and a collection pouch that is detachably connectable to the faceplate. The faceplate and pouch have alignable stoma-receiving openings, and a pair of thermoplastic coupling rings are secured to the faceplate and pouch about such openings for connecting the parts together. The advantage of such a two-piece appliance over a conventional one-piece appliance (in which a pouch and faceplate are permanently connected) is that a number of pouches may be used successively with a single faceplate. The user of a two-piece appliance may therefore leave a faceplate adhesively attached to the skin for an extended period, without the discomfort, inconvenience, and skin irritation that frequent removal and replacement of an adhesive faceplate may involve, and simply remove a used pouch and replace it with a fresh pouch whenever needed.
To be effective, however, it is critical that a two-piece appliance be free of leakage problems since even slight leakage of liquid, solid, or gaseous matter could cause considerable inconvenience and embarrassment to the wearer. Much effort has been expended in the past to develop coupling systems that are reliable and not likely to be inadvertently detached in use, are nevertheless easy to assemble and disconnect at will, and do not leak even when a number of pouch rings have been successively coupled and uncoupled from a single faceplate ring. While some existing appliances come closer than others to fully achieving these objectives, their effectiveness in doing so has generally come at the sacrifice of one further objective--that of providing a coupling assembly of low enough profile that it does not protrude an appreciable distance from a wearer's body and does not produce conspicuous bulges through a wearer's clothing.
For example, some two-piece appliances utilize a coupling system in which one of the rings is channel-shaped (in radial cross section) and the mating ring includes an annular rib that is receivable in the channel to make both sealing and latching contact with the channel's inner surfaces. Reference may be had to patents U.S. Pat. No. 4,419,100, GB 1,571,657, GB 1,583,027 and EP 0 089 138 for couplings of the channel-and-rib type. While such constructions may provide latching and sealing effectiveness, they are all of relatively high profile and fail to lie flat against a patient's body. A further disadvantage is that in some channel-and-rib couplings, liquid-tight (and gas-tight) sealing is achieved by means of a thin-deflectable sealing lip extending from the rib of the faceplate ring, with such sealing lip often contributing to a latching function. After a number of coupling and uncoupling procedures, wear and damage of the faceplate ring often occurs so that the deflectable lip is no longer capable of performing an effective sealing function. Usually such wear or damage goes unnoticed until leakage results.
Patent U.S. Pat. No. 3,528,420 also discloses a coupling in which the sealing and latching functions are performed in the same contact areas. Attachment security may be compromised and the sealing surfaces easily worn or damaged by successive attachment and removal of pouches. U.S. Pat. No. 4,610,676 and U.S. Pat. No. 4,610,677 disclose coupling systems in which the latching zones are located radially outboard from the sealing zones; however, the sealing surfaces nevertheless must make repeated and forceful contact, with the risk of possible wear and damage, when pouches are successively attached to and removed from the reusable faceplates.
Other references indicating the state of the art are U.S. Pat. Nos. 4,786,285, 4,828,553, 4,460,363, 4,808,173, 4,846,820, 4,359,051, 4,518,389, and 4,950,261; GB patents and published applications 1,586,823, 2,153,683, 1,586,824, 1,217,406, 2,190,841, 1,274,382, 2,147,810A, 2,173,403A, and 2,151,482A; International publications WO 91/01118 and WO 85/03427; and European patents and application 0 089 138, 0 142 259, and 0 429 199A.